Steve Eddy,
Care to discuss weaving a 3/8 inch diameter cotton cable for a commercial scheme? All pre dyed cotton thread, probably in 1k yard lengths, relatively often. PM me if you are interested. Not for cables by the way.
Bud
Care to discuss weaving a 3/8 inch diameter cotton cable for a commercial scheme? All pre dyed cotton thread, probably in 1k yard lengths, relatively often. PM me if you are interested. Not for cables by the way.
Bud
Hey JR - the cheap optical cable in question is very thin and black, came with some piece of gear, don't remember what. I love this cable because it's so bad.
I first noticed it running it into a DDX amp board. This is a "digital" amp. PCM to PWM direct. Uses a typical spdif receiver chip. I thought the amp or my speakers had gone bad, or my ears. Harsh, shrill, awful. No dropouts or anything, just rotten sounds. But put a better cable in (nothing special) and all was well. Put that bad cable back and it was crap again.
Later found that this amp board is very sensitive to clock issues - jitter. If the incoming signal isn't clean, neither is the clock. Result? Sounds rough. This was true for coax and optical. Finding the "right" cable helped a lot. Impedance mismatches again. No magic.
Don't know why the optical cable is so bad, but you may be right about reflections.
I first noticed it running it into a DDX amp board. This is a "digital" amp. PCM to PWM direct. Uses a typical spdif receiver chip. I thought the amp or my speakers had gone bad, or my ears. Harsh, shrill, awful. No dropouts or anything, just rotten sounds. But put a better cable in (nothing special) and all was well. Put that bad cable back and it was crap again.
Later found that this amp board is very sensitive to clock issues - jitter. If the incoming signal isn't clean, neither is the clock. Result? Sounds rough. This was true for coax and optical. Finding the "right" cable helped a lot. Impedance mismatches again. No magic.
Don't know why the optical cable is so bad, but you may be right about reflections.
And speaking of optical cables, a funny story. Video, sorry. But optical cable.
About 10 years ago I was working to install a new TV station. Cameras were upstairs, control room in the basement. The designer had spec'd in fiber optic to get the signal out of the cameras control units and down into the basement. All top end broadcast stuff.
One of our techs had just been to school to learn how to terminate fiber. He had his tools, his microscope, his polishing pads and pastes. Everything to make beautiful ends on the fiber cables. And he spent hours doing them. No signal loss, no sir!
Once it was all hooked up, the video looked awful. All blown out and overdriven. We couldn't figure it. So we called the manufacturer of the optical transmitters and receivers. We described the problem we were having. The tech on the other end finally asked "how long is your fiber run?" "Oh, maybe 300 feet", we said. He laughed and told us the units we had were meant for runs of several miles! We were seriously over driving the receivers.
Solution? Air gap attenuators. You know the little red rubber caps you see on some optical connectors? We had to cut those into a little red ring and insert them into the female connectors. "air gap" With the fiber end pulled out enough, signal losses made it all good. So much for all the careful termination and fiber polishing!
Cables can make a difference. 😉
About 10 years ago I was working to install a new TV station. Cameras were upstairs, control room in the basement. The designer had spec'd in fiber optic to get the signal out of the cameras control units and down into the basement. All top end broadcast stuff.
One of our techs had just been to school to learn how to terminate fiber. He had his tools, his microscope, his polishing pads and pastes. Everything to make beautiful ends on the fiber cables. And he spent hours doing them. No signal loss, no sir!
Once it was all hooked up, the video looked awful. All blown out and overdriven. We couldn't figure it. So we called the manufacturer of the optical transmitters and receivers. We described the problem we were having. The tech on the other end finally asked "how long is your fiber run?" "Oh, maybe 300 feet", we said. He laughed and told us the units we had were meant for runs of several miles! We were seriously over driving the receivers.
Solution? Air gap attenuators. You know the little red rubber caps you see on some optical connectors? We had to cut those into a little red ring and insert them into the female connectors. "air gap" With the fiber end pulled out enough, signal losses made it all good. So much for all the careful termination and fiber polishing!
Cables can make a difference. 😉
Member
Joined 2002
The old bits-is-bits agrgument?
The signal traveling in a digital audio cable is analog. Depending on how well the bumps are defined, significant timing errors -- jitter -- can result.
dave
In general shielding in real systems can be a quite complex matter. While some rules of thumb exist (and often do work) it is impossible to say in advance which cable/shield combination might be the right one without having measured which kind of interference radiation exists.
Electrostatic and/or magnetic coupling, which frequency range, which grounding scheme in the components that will be connected and so on.
Wishes
Ummm... I'm certainly no expert on digital systems, but doesn't the DAC have its own clock? The handwaves I've seen about digital cables are usually vague, "makes the receiver chip/powersupply/whatever work harder to recover the signal," not "causes jitter in the recovered signal."
Now, if a cable is truly awful, there won't be jitter, there will be out and out errors, as anyone who ever tried running an IMP off a 20 foot printer cable will have found out. This is not an issue for the usual audiophile short runs, but I could certainly see potential problems (which are not addressed by the snake oil digital ICs) in a studio setup.
Though agreed that they adopt the usual snake oil stuff in their ads, I've bought wire form them in the past (like all the silver wire in my phono preamp) and their prices were reasonable and they were reliable. So I can't fault them on that score.
Exactly! I think it was Hawksford and Dunn who showed that the jitter is even code dependent, ie correlated to the music. This happens with both AES/EBU and S/PDIF.
@SY: yes, if the DAC has a clean clock and in fact 're-clocks' the signal, that jitter can be very much attenuated or even completely removed, but it's there when the signal leaves the cable!
For the record: In my opinion, if you hear differences between digital cables, you have one spectacularly incompetent designed DAC...
jd
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But Jan, doesn't the DAC's clock take care of that up until the point where the transmission starts causing errors?
🙄
Unshielded, plain "twisted pairs" are substandard from just about any "interference radiation" perspective. And cotton braiding doesn't help either.
Will you please tell that to Bob Carver, I've heard very obvious differences in SQ between three purpose made digital cables when used between my CD Player and TG4 processor. 😉
I do however agree that it is possible to minimise jitter to the DAC but I also belief SPDIF is inherently a flawed format.
But to be fair at that point, Dunn investigated the interface problems and developed a method to measure the effects of various jitter amounts at the _analog_ outputs of DACs, so afair there was a lot of `spectacularly incompetent designed DACs ´around (in the professional world too) at that time. 🙂
And we have to admit, that this investigation only started several years of complaining about the sound quality delivered by these units.
And i think we can both remember what the `professional´ reaction on that audiophile complaints was (NO WAY, because of re-clocking, buffering etc. etc.) until Dunn investigated.....
And of course audibility of jitter is still controversial and that brings us to another favourite topic of mine, means "spectacularly incompetent designed listening tests" 🙂
Wishes
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While i of course tend to agree mostly, there are cases in which for example a coaxial cable is unshielded too and sometimes even a twisted unshielded pair could be better than a simple coax.
Ott and Morrison for example both provided some measurements for most cases.
It simply depends on to what extent shield currents and signal currents can be divided, what coupling mechanism from shield to signal wire exists and which interference is present (and in what frequency band).
Wishes
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Andre,
It's very simple: bit is bit, so as long as there is not a catastrophic loss of code, the data gets across correctly. And that will work even with chicken wire.
The jitter that comes into the DAC has a lot of sources, the transport, the digital processing, the cable, the supply interaction, etc etc. A 1st class DAC can almost completely remove that jitter. So if you have a 1st class DAC, the cable is no longer a factor in the final result.
Now I am aware that people report audible cable differences. But as far as I know they are always personal and anecdotal and never (AFAIK) controlled and statistically relevant. There are a LOT of conditions and circumstances that can lead to the perception of differences and the actual sound is only one of those conditions and circumstances. Therefore, the anecdotal/personal reports have almost no value to decide if there is or is not an audible difference.
And yes, there is a basic flaw in S/PDIF (and AES/EBU) that causes jitter, but as noted, a good DAC will make short shrift of that.
jd
The study I mean is this:
C41 IS THE AES/EBU/SPDIF DIGITAL AUDIO INTERFACE FLAWED?, Dunn, C. and Hawksford, M.O.J., 93rd AES Convention, San Francisco, preprint 3360, October 1992
which is downloadable from Hawksford's Essex University website.
IIRC, H and D measured the interface jitter at the recovered clock at the DAC, but as said, if the DAC has a clean clock of itself, that jitter will no longer be of any consequence.
To make it more confusing, there are actually TWO Chis Dunn's, and both have written on digital audio issues. One of them is deceased, however.
jd
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